In known blister lights, in which use is also made as luminous device of, inter alia, LEDs (light-emitting diodes), the quantity of heat produced during operation of the luminous device is usually transferred by convection into a gas, which is often air. In some known blister lights, the luminous device is assigned a heat sink starting from which the quantity of heat produced during operation of the luminous device is given off to the gas or air by convection. Because of the limited spatial conditions prevailing in blister lights, even blister lights equipped with a heat sink with low heat transfer resistance have a total heat transfer resistance of usually more than 30 K/W power loss.
In the use, known from the prior art, of LEDs mounted on PC plates, a heat transfer resistance of more than 150 K/W results between the barrier layer of the LEDs and the PC plate. In some automotive applications, a heat transfer resistance of the order of approximately 70 K/W is achieved. These high heat transfer resistances, which accompany maximum temperatures of the barrier layers that are usually of the order of magnitude of a little above 120° C., limit the current density possible and/or permissible during operation of the blister light. They thus produce, in a corresponding way, a limitation of the light-emitting power of the LEDs that can be achieved per unit of area of the barrier layer.
In the case of freely arranged lighting devices, for example traffic lights or the like, this limitation of the emitting power per unit of area is compensated by an increase in the area used for the emission of light and in the number of the light-emitting diodes. This enlargement of the light-emitting area is not practicable for blister lights, since blister lights are embedded in the traffic area. Further, since the emitting area of a blister light that is available in total for the emission of light is limited by the projection of the blister light above the surface of the traffic area, it is necessary for this projection to be as small as possible owing to a multiplicity of technically and mechanically conditioned requirements placed on the blister light.